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Personal Health; Protecting Children From Bugs That Bite

WITH the summer season now in full swing in most parts of the country and youngsters spending more of their waking hours out of doors often skimpily attired, biting insects are finding easy targets for the blood they need to reproduce. And parents once again are challenged to find the best way to protect their children from annoying and possibly dangerous bites from such critters as gnats, mosquitoes, biting flies, chiggers and ticks.

Product choices abound and continue to multiply. But all are not equally safe or effective.

In the current issue of Contemporary Pediatrics, a medical magazine for physicians, Dr. Adelaide A. Hebert, a professor of dermatology and pediatrics at the University of Texas Medical School in Houston, and Dr. Soni Carlton, now an intern at the university's Galveston branch, discuss the pros and cons of products currently available and the safest ways to use them.

Parents must always keep in mind that children are not just small adults; what may be safe for a grown-up is not necessarily safe for a child. A child's skin surface area relative to body size is far greater than an adult's and a child's skin is thinner, so any substance applied to and absorbed through the skin can have much more of an impact on a child.

This troublesome fact collides with the need to reapply repellents every few hours, since they are rubbed off by clothing and other objects and are lost to evaporation, wind, sweat, heat and water. Also, the new products that combine repellents with sunscreen require frequent reapplication to maintain the sunscreen's effectiveness.

The leading and still the most effective all-purpose repellent is one of the oldest products around: DEET, the popular name for the chemical N,N-diethyl-m-toluamine, used as a repellent since 1957. It is sold in concentrations of 4 percent to 100 percent as sprays, aerosols, gels, liquids, sticks and treated towels.

However, products used on children should not contain more than 10 percent DEET, the lowest effective dose. In high concentrations, which are most effective as repellents, DEET can be highly toxic to children. The Texas physicians noted that 13 youngsters under age 8 are known to have developed encephalopathy, suffering seizures and convulsions, after using too much DEET. Three children died, but the others recovered completely. Most of these incidents followed repeated applications of products containing 10 percent or 20 percent DEET.

DEET products can be applied directly to the skin, but it is safer with children to apply it to their clothing (it may, however, damage plastics, vinyl, spandex, rayon and acetate). The problem is, mosquitoes will bite any exposed skin that is not treated; DEET on the nose will not protect the cheeks or forehead. Avoid putting DEET near a child's eyes and mouth, on any cuts or abrasions, or on the hands of small children.

Citronella, a natural substance, is another time-honored repellent. It is the active ingredient in Avon's Skin-So-Soft, the bath oil that has acquired a sizable market as a repellent. Its protection is short-lived, however, and although safer than DEET, it is not as effective a repellent.

Another natural repellent said to be particularly effective in warding off mosquitoes is soybean oil. Two percent soybean oil is the active ingredient in Bite Blocker, which also contains a sunscreen. But Dr. Hebert said this product tends to sting the skin and has an unpleasant odor, which would discourage its use. Although rubbing the skin with kitchen soybean oil has not yet been formally tested as a repellent, it would be safe for children and may be worth a try.

Many parents are more concerned about ticks than mosquitoes, since some ticks -- the deer tick in particular -- carry the agent that causes Lyme disease. Permethrin, found in the tick repellents Permanone and Duranon, is highly effective, far better than DEET, Dr. Hebert said. It not only repels ticks; it kills them on contact.

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But while permethrin is the active ingredient in products put on skin to treat scabies and lice, it has not been tested for safety as a repellent applied to skin. Therefore, experts insist that permethrin repellent should never be applied directly to a child's skin. Instead, it should be sprayed only on clothing and shoes and equipment like tents, sleeping bags and netting. It will remain effective through several washings, the physicians wrote. Dr. Hebert said Permanone, which is generally not sold in pharmacies and supermarkets, can usually be found in hardware, garden supply and sporting goods stores.

For the most complete protection against ticks, Drs. Hebert and Carlton suggested applying a DEET-containing product to skin and a permethrin product to a child's clothing. To minimize exposure, repellent should be washed off with soap and water when the child comes in.

The Combination Products

Clever manufacturers have come up with a way to kill two bugs with one stone. Several now make products that combine an insect repellent with a sunscreen. However, according to a study published last year in the journal The Lancet, the presence of DEET, found in several combination products, can undermine the effectiveness of the sunscreen, reducing its S.P.F. (sun protection factor) rating by about a third. Check the label before you buy. If you choose a combination product with DEET, it would be best to buy one with a high S.P.F. -- 30 or more -- since you may be getting less than the stated sun protection.

Also, keep in mind that it would not be safe to reapply a DEET-containing product to a child's skin every two hours, as may be needed to get adequate sun protection. The Texas doctors suggest instead using a combination product made with citronella as the repellent. Or you can try adding soybean oil to your child's favorite sunscreen.

One final point: It is also worth remembering that no insect repellent is very effective against stinging insects like bees, yellow jackets and other wasps and fire ants. Nor do black flies, which are biters, seem to have much respect for repellents currently on the market. (Dr. Hebert said that DEET does repel black flies, but you can't prove it by my experience.) Avoiding such insects is the best defense.

Children should be taught not to disturb stinging insects and especially not to flail wildly at them; these insects use their stingers for defense, not procreation; they sting when they feel threatened. If your child is stung, consult a doctor to prescribe a steroid or to remove a stinger that was left behind.

Black flies are seasonal biters, usually attacking in late spring in cooler regions like New England and the Upper Midwest. If you can't avoid black fly territory during the biting season, covering up with loose-fitting clothing is probably the best defense, followed by small amounts of repellents containing 2-ethyl-1,3-hexanediol, an ingredient found in OFF! and 6-12.

Or, as my family discovered on a June camping trip in Minnesota, staying immersed in water works, too.

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A version of this article appears in print on July 7, 1998, on Page F00007 of the National edition with the headline: Personal Health; Protecting Children From Bugs That Bite. Order Reprints|Today's Paper|Subscribe